hw/xen-hvm: Add a mapcache arg to xen_register_ioreq() Add a mapcache argument to xen_register_ioreq() allowing the caller to optionally disable the mapcache. All callers still call it with mapcache = true so there's no functional change yet. Signed-off-by: Edgar E. Iglesias <edgar.iglesias@amd.com> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>